Overload safety switch apparatus

ABSTRACT

An overload safety switch apparatus. Direct switch-to-load movable connection-contact means are provided for supervision of the load hoisting operation, and resilient load-sensing means are provided for use in the safety switch apparatus, to thereby provide an overload safety switch device which supervises loadlifting electrically-operable hoist operation to interrupt the electrical hoist circuit in the event that the lift load exceeds the programmed maximum safe load weight, to safely shut down the hoist operation thereby.

United States Patent 1191 Ridge et al.

[ 1 May 15, 1973 [54] OVERLOAD SAFETY SWITCH APPARATUS [76] Inventors: Charles K. Ridge, 71 Norwood Avenue, Upper Montclair; Jack R. Allen, 16 Oak Tree Lane, Bloomfield, both of NJ.

[22] Filed: Oct. 18, 1971 [21] App1.No.: 190,123

[52] US. Cl ..200/85 R, 212/39, 254/174 [51] Int. Cl ..H0lh 3/14 [58] Field of Search ..200/85; 212/39 DB,

212/39 MS; 254/173 R, 174 R [56] References Cited UNITED STATES PATENTS 7/1963 12 1941 l-laniquet ..212 39 MS Silberger ..2 1 2/39 DB FOREIGN PATENTS OR APPLICATIONS 1,189,329 3/1959 France ..254/173 R 814,642 6/1959 Great Britain ..212/39 DB Primary ExaminerDavid Smith, Jr. A ttorney-Harry Sommers et al.

[57] ABSTRACT 2 Claims, 2 Drawing Figures PATENTEU W1 975 INVENTORS CHARLES K, FRI 55 CK R. ALL. N

W119i M ATTORNEYS OVERLOAD SAFETY SWITCH APPARATUS BACKGROUND OF INVENTION This invention relates generally to safety switches, and more specifically relates to an overload safety switch apparatus which interrupts the electrical hoist circuit to provide for safe system shutdown in the event that the load-weight exceeds the preset safe lift weight.

Hoisting devices of the type intended to provide continuous load lifting, and which are electrically operable, commonly are provided with indirect switch-toweight connection means to divert and transfer force components from the load-weight direction of movement. The performance of hoist system safety shutdown operation heretofore required the use of a multiplicity of operating elements to divert the force components, with increased dangers of element breakdown, with resultant safety system failure and consequent danger to operating personnel and system equipment as a result thereof.

Complex load sensing mechanisms required constant testing and repair with consequent inconvenience, inefficiency and loss of economy of operation resulting therefrom.

In accordance with the foregoing, it may be regarded as among the objects of the present invention, to provide movable contact-connection means to enable direct and complete system shutdown on excessive load lift weight for safety and efficiency of operation.

It is a further object of the invention, to provide resilient load-sensing means, which accurately sense excessive load weight, and efficiently respond to removal thereof by resetting for continued responsive safety apparatus operation.

Now in accordance with the present invention, the foregoing objects, and others as will become apparent in the course of the ensuing specification, are achieved in an overload safety switch apparatus operable, as will be described below, so that system shutdown of hoisting excessive load-weight is achieved by the provision therein of movable contact-connection means and resilient load-sensing means, thereby increasing the safety, efficiency, and utility of the electrically operable hoist apparatus for the hoisting operations performable thereby.

BRIEF DESCRIPTION OF THE DRAWINGS The invention is diagrammatically illustrated, by way of example, in the appended drawings, wherein similar reference characters indicate like parts, in which:

FIG. 1 is a front elevational view of an overload safety switch apparatus embodying the invention; and

FIG. 2 is a side elevational partly-sectional view thereof, taken at line 2--2 of FIG. 1.

DESCRIPTION OF PREFERRED EMBODIMENTS In accordance with the preferred mode of practicing the invention, the overload safety switch apparatus 11 (FIG. 1 for example, comprises a housing 12, a switch 13, movable contact-connection means 14, resilient load-sensing means 15, support means 16, and load 7 support 17 (shown in broken view thereof).

The switch 13 is comprised of contact surface 30 and circuit connection posts 31, 31', 31", mounted to housing 12 by mounting screws 32, 32' through mounting apertures 33, 33'.

The movable contact-connection means 14, comprises (FIG. 1), for example, an eye-bolt connector 40 with a bottom loop portion 41, a lower shaft portion 42, an upper shaft portion 43, and an upper contact surface 44.

The resilient load-sensing means 15 comprises, for example (FIG. 2), disc spring sensors 50, upper retention means 51, and lower retention means 52. The upper retention means 51 includes upper retainer nut 53 and upper and lower washers 54, 56, and lower retention means 52 includes lower retention nut 55. The support means 16 comprises, for example, support screws 60, which extend through support apertures 61, 61'.

In operation, for example, the overload safety switch apparatus may be utilized to supervise an electricallyoperable hoist for safe operation thereof, by interposing the safety switch apparatus in the electrical hoist circuit. The housing 12 may be mounted on a suitable elevated surface by support screws 60, 60' extending through support apertures 61, 61 in the housing rear wall 23. The switch 13 is mounted to the housing rear wall 23 by mounting screws 33, 33' which extend through mounting apertures 32 (shown), 32 (not shown), and the movable contact-connection means 14 are mounted in the housing 12 with the resilient load sensing means 15 positioned thereon by extending the lower shaft portion 42 and upper shaft portion 43 of the eye bolt connector 40 through housing 12 bottom vertical aperture 25 and central vertical aperture 24 respectively, with the resilient load-sensing means 15 upper retainer nut 53, upper retainer washer 54, disc spring sensors 50 and lower retainer washer 56 positioned between the housing 12 bottom wall 22 and the eye bolt connector 40 bottom loop portion 41. The disc spring sensors 50 are collapsible and resilient, and the sensitivity thereof to load weight may be preset by varying the number of such members utilized.

When the load lift weight supported on the load support, which extends through the eye bolt connector 40 bottom loop portion 41, exceeds the preset disc spring sensors compression weight, the upper contact surface 44 of the eye bolt connector 40, normally urged into contact with the switch 13 contact surface 30, will be directly pulled by the excessive load weight out of contact with the switch 12, thereby interrupting the electrical hoist circuit, to thereby automatically shut down the hoist operation in order to prevent further hoisting of the excessive load weight which would result in system breakdown, such as load support breakage, with resultant danger to personnel and property. A manual override may be provided (not shown) to lower the excessive load weight in safety. Whenthe weight being hoisted is not excessive, the eye bolt connector 40 upper contact surface 44 remains in contact with the switch 13 contact surface 30 and the hoist electrical power is provided without interruption.

It is thus seen that the provision of features described above enables the safe and efficient operation of a hoist lifting apparatus with movable contact-connection, and resilient load-sensing, to thereby enable use thereof for a wide range of operations with optimum safety, efficiency and convenience.

While the present invention has been particularly described in terms of a specific embodiment thereof, it will be understood in view of the present disclosure, that numerous modifications upon the invention now are enabled to those skilled in the art, which variations, in propriety, yet reside within the true scope of the instant teaching. Accordingly, the invention is to be broadly construed, and limited only by the scope and spirit of the claims now appended hereto.

We claim:

1. In an apparatus for controlling operation of an electric hoist circuit dependent on the load supported on the hoist exceeding a predetermined weight;

a. a housing adapted to be secured to a fixed support,

said housing including a rear wall,

b. a wall secured to and extending angularly from the rear wall, intermediate the ends of the rear wall, and having an aperture therethrough,

c. a switch for the electric hoist circuit, said switch being mounted in spaced relation to the top of the angularly extending wall and in axial alignment with the aperture therethrough, and having a switch contact surface controlling operation of said switch and thereby controlling the electric hoist circuit,

d. elongated switch control means for movably contacting the switch contact surface at one end and for connection with the load at the other end, said means being movably positioned in the aperture in the angularly extending wall and reciprocable therein,

e. means for resiliently sensing and responding to the load weight, said means having opposite ends, one

of said ends being positioned atop the angularlyextending wall,

f. said resiliently sensing and responding means being movable upon application of weight load thereto,

g. retaining means adjustable movable along said elongated means and into engagement with the resiliently sensing and responding means for urging the latter onto the top of said angularly extending wall, to the degree so predetermined by the position of the retaining means on the elongated switch control means, to thereby adjustably predetermine the compression of the resilient means to the degree required by the load so connected to said elongated switch control means, and

h. lower retainer means engaging the elongated switch control means and urged into engagement with the bottom of the angularly extending wall by the action of the resiliently sensing means on said elongated switch control means.

2. In an apparatus as set forth in claim 10,

a further wall extending from the rear wall in spaced relation to the first mentioned wall so extending therefrom, said further wall having an aperture therethrough,

said elongated switch control means comprising a shaft having a threaded portion for threaded engagement by said retaining means for adjustment of said retaining means along the shaft portion for so engaging the resiliently sensing and responding means and so adjusting the compression of the resilient means according to the load to be secured to said switch control means. 

1. In an apparatus for controlling operation of an electric hoist circuit dependent on the load supported on the hoist exceeding a predetermined weight; a. a housing adapted to be secured to a fixed support, said housing including a rear wall, b. a wall secured to and extending angularly from the rear wall, intermediate the ends of the rear wall, and having an aperture therethrough, c. a switch for the electric hoist circuit, said switch being mounted in spaced relation to the top of the angularly extending wall and in axial alignment with the aperture therethrough, and having a switch contact surface controlling operation of said switch and thereby controlling the electric hoist circuit, d. elongated switch control means for movably contacting the switch contact surface at one end and for connection with the load at the other end, said means being movably positioned in the aperture in the angularly extending wall and reciprocable therein, e. means for resiliently sensing and responding to the load weight, said means having opposite ends, one of said ends being positioned atop the angularly-extending wall, f. said resiliently sensing and responding means being movable upon application of weight load thereto, g. retaining means adjustable movable along said elongated means and into engagement with the resiliently sensing and responding means for urging the latter onto the top of said angularly extending wall, to the degree so predetermined by the position of the retaining means on the elongated switch control means, to thereby adjustably predetermine the compression of the resilient means to the degree required by the load so connected to said elongated switch control means, and h. lower retainer means engaging the elongated switch control means and urged into engagement with the bottom of the angularly extending wall by the action of the resiliently sensing means on said elongated switch control means.
 2. In an apparatus as set forth in claim 10, a further wall extending from the rear wall in spaced relation to the first mentioned wall so extending therefrom, said further wall having an aperture therethrough, said elongated switch control means comprising a shaft having a threaded portion for threaded engagement by said retaining means for adjustment of said retaining means along the shaft portion for so engaging the resiliently sensing and responding means and so adjusting the compression of the resilient means according to the load to be secured to said switch control means. 